I have a few mkv files which contains subtitles.When i play them with xine i can select the subtitle but when i use Xine_player then i cannot select subtitles.Can i change the default somewhere? When i start xine from the commandline and giving the option -u0 is enough to enable the default subtitle from track 0.

Maybe take a look at this script - /usr/pluto/bin/SpawnDevice.sh it starts xine_player (among other devices) so maybe you could modify something to add that option (but it would then apply to all video media)